GPON动态带宽分配算法的研究

【作者】 张力；

【导师】 胡钢；

【作者基本信息】 电子科技大学 ， 通信与信息系统， 2006， 硕士

【摘要】 ITU-T推出的G.984.x系列标准对规范GPON的实现产生了重要影响,但是标准仅对GPON的基本结构和协议进行了详细的规定。如果需要将GPON投入实际的商业运营,GPON还有很多关键技术需要研究。由于能够高质量、高效率的传输不同QoS要求业务这一特点是GPON较其它无源光接入网技术最大的优点,所以研究出一套即简单实用又能够满足业务QoS要求的高效上行动态带宽分配和利用算法将是GPON成功的关键。本文基于对ITU-T标准的详细分析,结合对GPON特有的带宽优先级和T-CONT复用方式的理解,借鉴了一些基本的公平性分配机制,经过反复论证和试验,提出一套GPON上行带宽分配和利用算法。该套算法由两大部分组成:一是OLT端针对T-CONT的带宽分配算法,其功能是依据各个T-CONT的拥塞报告,结合网络整体负载状态,完成四种类型带宽在不同类型、不同拥塞状态的T-CONT之间的分配;一是ONU端针对T-CONT的填充算法。后者又根据T-CONT复用业务的数目和业务延时特性要求分为三种情况:单个业务复用到单个T-CONT中、多个相同延时特性要求的业务复用到单个T-CONT中和多个不同延时特性要求的业务复用到单个T-CONT中。在完成对算法行为的介绍以后,本文在OPNET环境下对这套算法作用下的GPON上行信道进行了建模仿真,并主要从业务的帧延时特性和实际得到的带宽两方面考察该套算法对业务QoS的保证。仿真结果清晰的表明,这套算法即能够支持ITU-T标准中规定的各种T-CONT的传输特性,也能够在多个业务复用到同一个T-CONT的情况下保证各个业务之间的公平性和QoS要求。从仿真结果看,这套算法达到了设计初衷,能够通过T-CONT同时传输不同QoS要求的业务。最后,本文还对该算法在仿真过程中出现的一些现象进行了深入分析,发掘其内在的原因,得出了几个定性的推论,并且在此基础上指出了下一步的研究方向。更多还原

【Abstract】 The G.984.x standards established by ITU-T have important impact on the realization of GPON, but the standards just specify the basic architecture and protocol stack of GPON. There are several key techniques which need further study before GPON is used for commercial purpose. Because the most valuable advantage of GPON is that it can transmit services which require different QoS guarantees at the same time, the dynamic bandwidth allocation and utilization algorithm which can be easily realized and provide different QoS support will be the key to success of GPON.This article is based on the intensive analysis of ITU-T standards and then provides a suit of algorithms which focuses on the problem of upstream bandwidth allocation and utilization and support the bandwidth priority mechanism which specified by the ITU-T standards, too. This suit of algorithm constitutes two parts: one is the bandwidth allocation algorithm against T-CONT, which is executed in OLT; the other is the bandwidth utilization algorithm against T-CONT, which is executed in ONU. The latter will be divided into three cases: single service into single T-CONT, multiple services with the same delay requirement into single T-CONT, and multiple services with different delay requirements into single T-CONT.After the explanation of the processing procedure of the algorithm, this article modeled the GPON upstream channel operated by it. The full and accurate simulation under OPNET proves that the algorithm can well support all kinds of T-CONT which specified by ITU-T standards, and can guarantee the QoS requirement and the equitableness between multiple services which are multiplexed into the same T-CONT at the same time. In short, the suit of algorithm completely satisfies the original intention, that is, to transmit services with different QoS requirement through T-CONT at the same time. At the last, this article gives further explanation against some phenomena in the simulation result and states the work orientation in the future.更多还原